I have seen plenty of 1930-50 era guns that have just taken on that brownish patina on the metal, but had very little actual wear. I did have a 1930 Stevens SXS 410 that had one barrel fired so much that the sear eventually wore uneven and had to be replaced, but the hinge, barrel etc were all fine. I would say you will have to replace the internals long before you need worry about latch & hinge.